atttmixttvt a



United States Patent PROCESS OF COATING ALUMINUM AND PRODUCT Herschel Greer McMorris and Florian H. McCall, Clearwater, 'Fla., 'assignors, by mesne assignments, to -Myr'on P. Laughlin, St. Petersburg, Fla.

No Drawing. Application May 17, 1954 Serial No. 430,422

4 Claims. (Cl. 117-8) This invention relates to metal treating, and more especially to the surface treatment of aluminum and allied metals.

The main protection of aluminum surfaces has heretofore been accomplished mainly through some variation "of 'sul'phati'ng or anodizing processes. It has been custornary to polish aluminum for selling purposes andthen to allow it to sulphate naturally in the hands of the purchaser, a process which often resulted in the blackish sulphate rubbing oflf on clothing and the like when aluminum was used in furniture, and particularly when aluminum was used in surgical appliances and supports. Plating and anodizing, on the other hand, were so expensive as to bar their use for all practical purposes when a popular priced article was to be produced.

It is the primary purpose of this invention to provide means where aluminum and the like may be surface protected at low cost and without the expensive equipment and materials essential to plating and anodizing.

It is a second purpose of this invention to provide process and means for so treating the surfaces of the softer metals that substantially any colored surface appearance may be provided without the expense of electric deposition, while still providing substantially permanent results.

It is a main purpose of this invention to provide means whereby the surface of such softer metals may be protected and colored, while such metals are in their original mill forms and before such metals are fabricated and to provide such protection of coloring in a form which will withstand bending and machining during fabrication without substantial damage, so that a substantial further reduction in cost of manufacture is effected.

It is a special purpose of this invention to provide a surface protection for aluminum which will permit its use in surgical appliances, such as crutches and paraplegic supports without the staining of bandages and the like which has heretofore barred its use, so that such patients may enjoy in full the benefit of substantially lighter and more easily manipulated support for their infirmity.

The applicants process most briefly put comprises impressing a pattern of relatively small depressions or pits into the metal surface, then inserting material which may contain color into said pits and then preferably, but not necessarily, applying a protective coating over the material in the pits.

The pits may be rapidly produced by a variety of methods and are preferably of greater dimension across than lengthwise of the metal, but of such fineness as to present a substantially continuous surface to the normal eye and to be readily apparent only under magnification. The fineness of such pit pattern being substantially that which is less than a printers screen of eye visability as a measure thereof. Sand, fine particles of harder metals, carborundum and the like impelled by air, or mechanical impetus are feasible methods of producing the pits economically and are examples of the methods already Patented July 14, 1959 ice available While many alternatives will appear to those skilled in the arts.

The inserted materials may be simple coloring compounds including the anilines, metals, mineral colors, such as the chromes and inert products, such as the silicates and sands all ground fine enough so that they may be encompassed in the pits and in semi plastic form; thus these materials will preferably not project substantially above the metal surface sothat wiping over or ordinary frictional contact with the surface will not tear them from the binding substances which in cooperation with mechanical cohesion, hold such materials in the pits. The pits being of such fineness and so patterned, as above stated, when so filled with material cause the surface of the metallic object to which our method has been applied to present to the eye an unbroken appearance which is that ofthe insert materials rather than that of the original metal although, particularly in the case of aluminum, the metal forming the pit walls is in a slight part visible and provides light reflective surfaces of sufiicient area to proslightly less than a printers minimum screen of three thousand pits per square inch and preferably in the neighborhood of two thousand pits to the square inch.

At the same time, from knowledge 'old in the typographic arts, it will be apparent that the measure of fineness best adapted to the performance of this invention as a pit pattern will be slightly less than a printers minimum screen of 3000 pits per square inch and prefer ably in the range between 60 depressions per lineage and 300 depressions in the same space, the whole number in a given area preferably being not less than 2000 depressions per square inch leaving the actual metal area between the pits so small, relatively speaking, that if the inserted material be non-sulphating, the whole surface will show a minimum of sulphated surface, while the reflective effect of the metal area will still be sufficient to produce the luster which has been described.

It will also be seen that with the coloring or protective material divided into such minute pockets as has been described, the metal may be treated before it is bent and fabricated, and that such bending and working will not stress a substantial length of outer surface (as would occur in previous methods where the color coat is spread over the whole metal surface) but will rather alter very slightly the spacing of the pits While the inserted material lies undisturbed therein. This slight change in the spacings between pits around the outer circumference of the bend will not substantially alter the appearance of the metal articles since the whole disturbance is beyond the visual range and practically invisible. Thus, no cracking of the finish or peeling produced by color coat tearing loose from the metal is found and the finish appearance remains unchanged.

It will be manifest to those skilled in the finishing of objects that the material inserted in the pits will ordinarily have binding and adhesive components and that such material may be applied by spraying, rubbing, dipping or other deposit means and that after such application and insertion the material will bond itself into the individual pits and adhere therein, but in certain instances we prefer to coat the entire outer surface with film, such as lacquers, varnishes and plastics of an elastic or semielastic nature and our process greatly aids such outer coats by providing a multitude of bonding points rather than a single large area, thus relieving such outer coat of much of the strains formerly involved while at the same time assuring that rupture of a single bonding point will not spread and so free the whole that cracking and peeling of the entire finish results.

It Will be clear that many changes and modifications may be made in the embodiment of our invention and within the scope of the appended claims.

What we claim is:

1. An aluminum surface treating and coloring process which includes mechanically removing by means of impelled hard particles closely spaced particles from the' aluminum surface to produce a pit pattern of not less than 60 depression lines per linear inch transverse to the longest surface dimension and filling such pits with color to produce a substantially solid color effect upon the viewing eye.

2. The method of protecting and coloring a substantially white non-ferrous metallic aluminum surface which comprises pitting the said surface by means of impelled hard particles to a uniform density greater than 300 lines pits per inch, then uniformly loading said pits with a coating material then removing any excess material projecting from such pits, whereby a broken sub-surface coating protected from contact by the unpitted portions of the metal surface but having loaded pits of such density for a given area as to provide a substantially unbroken appearance to the unaided eye is provided.

3. As a product of the above process, aluminum furniture members having surfaces pitted to a pit density of not less than two thousand pits per square inch and having such pits loaded with a coloring material.

4. The method of producing a lustrous substantially white colored aluminum metal surface upon metal objects having a natural light reflective approaching white which comprises removing metal in a multiplicity of areas which are to hold the color by means of impelled hard particles to depths at least substantially equal to each areas surface area but leaving light reflective areas of the natural metal therebetween in close alternative pattern below visual separation, then replacing a substantial part of the removed metal in each removed area with material of another color reflective than that of the original metal object and removing excess coating material from the metal surface so that such color container areas are regularly disposed between said areas of naturally light reflective character and light striking the whole is reflected in a main portion by the colored areas to produce an eye effect of that color modified lightened and illuminated by that portion of the light reflected by the aforesaid metal areas left therebetween.

References Cited in the file of this patent UNITED STATES PATENTS 1,983,720 West Dec. 11, 1934 FOREIGN PATENTS 105,878 Australia Nov. 18, 1938 490,377 Canada Feb. 10, 1953 OTHER REFERENCES Protective Coatings for Metals, Burns and Schirch, American Chemical Society, Monograph Series, Reinhold 0 Pub. Co. New York, 1939, pages 30, 33, 312, 313, 314, 

1. AN ALUMINUM SURFACE TREATING AND COLOURING PROCESS WHICH INCLUDES MECHANICALLY REMOVING BY MEANS OF IMPELLED HARD PARTICLES CLOSELY SPACED PARTICLES FROM THE ALUMINUM SURFACE TO PRODUCE A PIT PATTERN OF NOT LESS THAN 60 DEPRESSION LINES PER LINEAR INCH TRANSVERSE TO THE LONGEST SURFACE DIMENSION AND FILLING SUCH PITS WITH COLOR TO PRODUCE A SUBSTANTIALLY SOLID COLOR EFFECT UPON THE VIEWING EYE. 